Role of ING4 in human melanoma cell migration, invasion and patient survival.

Inhibitor of growth (ING) 4 has been reported as a tumor suppressor and shown to diminish colony-forming efficiency, induce p53-dependent apoptosis and arrest cell cycle at G(2)-M phase. In this study, we investigated the role of ING4 in human melanoma pathogenesis. Using the tissue microarray technology, we found that ING4 expression is significantly decreased in malignant melanoma compared with dysplastic nevi (P < 0.0001, chi(2) test) and reduced ING4 staining is associated with melanoma thickness, ulceration (P = 0.034 and 0.002, respectively, chi(2) test) as well as poor overall and disease-specific 5-year survival of primary melanoma patients (P = 0.0002 and 0.001, respectively, chi(2) test). Cox regression analysis revealed that reduced ING4 staining is an independent factor for the poor prognosis of patients with primary melanomas. Furthermore, we found that overexpression of ING4 suppressed cell migration by 63% and inhibited the activity of Ras homolog gene family member A (RhoA) small GTPase protein and Rho-associated kinase (ROCK)-mediated formation of stress fiber in melanoma cells. Moreover, our data showed that overexpression of ING4 inhibited melanoma cell invasion by 43% compared with the control (P = 0.006, t-test) and ING4-overexpressing melanoma cells showed significantly reduced activity of matrix metalloproteinase (MMP)-2 and MMP-9. Taken together, this study highlights the importance of ING4 in melanoma pathogenesis and ING4 may serve as a promising prognostic marker and a potential therapeutic target for human melanoma.